Trackballs which are used in such environments may require cleaning of one or more parts of the trackballs. For instance, a ball, a housing, a bearing element and/or another part of a trackball may need to be wiped, sluiced or sprayed with fluid to remove accumulated dirt, oil, water and/or other substances. This can be particularly important if the trackball is used in medical environments in which the trackball comes into contact with patients or medical practitioners, whose health could be jeopardised if bacteria or viruses, for example, contaminate the trackball.
An example of a conventional trackball 11 is illustrated in FIGS. 1A and 1B. Like other conventional trackballs, the trackball 11 includes a ball 13 and a plurality of buttons 15 that act as mechanical function keys.
The ball 13 of trackball 11 is retained within a housing of the trackball 11 by a retaining ring 17. As well as retaining the ball 13 within the housing of the trackball 11, the retaining ring 17 may control or affect the force a user of the trackball 11 needs to apply to the ball 13 to cause the ball 13 to rotate relative to the housing. This force may be referred to as a “tracking force”. For instance, the retaining ring 17 may be in direct contact with the ball 13 such that there is friction between the retaining ring 17 and the ball 13. Alternatively, an intervening component or intervening components, such as a ball seal and/or a sponge, may be located between the retaining ring 17 and the ball 13 such that there is friction between a component and the ball 13. The magnitude of the friction may affect how easy it is for the user to rotate the ball 13 relative to the housing. To make cleaning the trackball easier, the retaining ring 17 may be removable (e.g. through a twisting unlocking motion or otherwise) to allow the ball 13 and/or other components to be removed for cleaning.
The buttons 15 and retaining ring 17 may be positioned adjacent to one another or to other components of the trackball 11. However, this leaves gaps 19 between the ball 13, the buttons 15, the retaining ring 17 and/or other components of the trackball 11. The dirt, oil, water and other substances referred to above can accumulate in these gaps. The gaps are difficult to clean and therefore present a hygiene risk as well as an opportunity for substances which can damage the trackball 11 to find their way into the trackball 11. Such substances may become trapped underneath the retaining ring 17 and/or underneath the buttons 15.
It is desirable to provide a trackball which overcomes or goes some way towards overcoming the problems discussed above.